The invention relates to a centrifugal pump with an axial inlet and an inflow guide device mounted upstream of the impeller, which guide device has several fixed guide vanes, which on the side facing the impeller each have an edge pointing towards or away from the direction of rotation of the impeller.
Centrifugal pumps with an axial inlet often have an inflow guide device mounted upstream of the first impeller. Their purpose is to remove a possible whirl from the transported fluid, such that an axial flow is present downstream of the inflow guide device.
The inflow guide device can be composed of several guide vanes, disposed uniformly around the perimeter of the inlet. The guide vanes can be attached to each other in the axis of the inlet and thus form a star or cross.
Inflow guide devices are known from DE 471 149 and DE 649 668 whose blades can be curved towards or away from the direction of rotation of the impeller in order to adapt to particular inflow conditions or to generate them. The curvature is bow shaped and extends in each case with the same axial length to the entire radial span of the blade. Here, when compared with the blade, the curvature has only a limited axial length.
In contrast to the previously described inflow guide device, which is equipped with seven blades and was relatively expensive, nowadays inflow crosses are preferred, that is, inflow guide devices comprising only four blades. These devices, inexpensive in themselves, are hardly able, however, to reduce an inherent disadvantage of the axial flow centrifugal pumps, the instability present in the pump's steady state characteristics. It is therefore the object of the invention to achieve such a reduction for a centrifugal pump of the type described above and on the whole to improve the flow conditions.